Upon logging in to your WP Admin, I saw that Cornerstone is not listed in your plugins so I went to X > Validation so X could install Cornerstone automatically. But, X could not install Cornerstone because the cornerstone folder already exist in your plugins folder.
I deleted the cornerstone folder and went to X > Validation but I got an error. I logged in to your server and found out that you've not installed X correctly. It should be installed directly under the themes folder and not in a sub-folder.
I moved X to the themes folder and X now successfully installed Cornerstone.
I then visited a page in Cornerstone and it works fine (see secure note). If it does not still work on your end, please provide the specific URL of the page so we could investigate. Since you're using WPML, also tell us if it does not work for all languages.
And since you're using Multisite, update X to the latest version but this time, follow the correct installation procedure.